Since the pioneering discovery of Ecke et al., U. S. Pat. No. 2,831,898, it has been possible to alkylate phenols selectively in the ortho position by reaction of a phenol having an open ortho position with an olefin, preferably a di-substituted (i.e. secondary) or tri-substituted (i.e. tert-olefin), in the presence of an aluminum phenoxide catalyst (i.e. an aluminum compound having at least one phenoxide or alkylphenoxide group bonded to aluminum). Following the alkylation it is necessary to deactivate the catalyst to prevent dealkylation and isomerization. Since the products are conventionally recovered by distillation, it is also necessary to remove the aluminum compounds to avoid pluggage of the distillation column. In a conventional process this can be accomplished by washing the completed alkylation mixture with a dilute aqueous acid solution such as dilute H.sub.3 PO.sub.4, HCl or acetic acid. This results in a spent aqueous wash solution which contains phenol and/or phenolic compounds and aluminum salts which present a formidable disposal problem.
Attempts have been made to circumvent the wash step by precipitating the aluminum phenoxide in a manner that permits removal of the aluminum containing residue by filtration. This is a difficult goal to achieve because aluminum compounds under neutral or basic conditions have a propensity to form gels which quickly plug any filter medium.
Geddes, U.S. Pat. No. 3,652,685, describe a method of catalyst removal in which a minimal amount of only 3-6 moles of water per mole of aluminum phenoxide are added to the alkylation mixture followed by filtration at 90.degree.-160.degree. C. in a pressure filter.
Katsumoto, U.S. Pat. No. 3,970,708, describe a modification of the Geddes process in which a neutral inorganic salt, e.g. sodium sulfate, is added to the reaction mixture along with the water to improve filtration rate.
Adigamov et al., U.S. Pat. No. 4,232,176, describe another method for removing the aluminum-containing catalyst in which a 3-20 molar excess of water based on aluminum is added to the reaction mixture which is heated to the critical range of 165.degree.-250.degree. C. under vacuum to form meta-aluminate. This is said to be readily removed by filtration.